Differential costs of reproduction in females and hermaphrodites in a gynodioecious plant

BACKGROUND AND AIMS: Plants exhibit a variety of reproductive systems where unisexual (females or males) morphs coexist with hermaphrodites. The maintenance of dimorphic and polymorphic reproductive systems may be problematic. For example, to coexist with hermaphrodites the females of gynodioecious species have to compensate for the lack of male function. In our study species, Geranium sylvaticum, a perennial gynodioecious herb, the relative seed fitness advantage of females varies significantly between years within populations as well as among populations. Differences in reproductive investment between females and hermaphrodites may lead to differences in future survival, growth and reproductive success, i.e. to differential costs of reproduction. Since females of this species produce more seeds, higher costs of reproduction in females than in hermaphrodites were expected. Due to the higher costs of reproduction, the yearly variation in reproductive output of females might be more pronounced than that of hermaphrodites. METHODS: Using supplemental hand-pollination of females and hermaphrodites of G. sylvaticum we examined if increased reproductive output leads to differential costs of reproduction in terms of survival, probability of flowering, and seed production in the following year. KEY RESULTS: Experimentally increased reproductive output had differential effects on the reproduction of females and hermaphrodites. In hermaphrodites, the probability of flowering decreased significantly in the following year, whereas in females the costs were expressed in terms of decreased future seed production. CONCLUSIONS: When combining the probability of flowering and seed production per plant to estimate the multiplicative change in fitness, female plants showed a 56 % and hermaphrodites showed a 39 % decrease in fitness due to experimentally increased reproduction. Therefore, in total, female plants seem to be more sensitive to the cost of reproduction in terms of seed fitness than hermaphrodites

Zfp148 deficiency causes lung maturation defects and lethality in newborn mice that are rescued by deletion of p53 or antioxidant treatment.

The transcription factor Zfp148 (Zbp-89, BFCOL, BERF1, htβ) interacts physically with the tumor suppressor p53 and is implicated in cell cycle control, but the physiological role of Zfp148 remains unknown. Here we show that Zfp148 deficiency leads to respiratory distress and lethality in newborn mice. Zfp148 deficiency prevented structural maturation of the prenatal lung without affecting type II cell differentiation or surfactant production. BrdU analyses revealed that Zfp148 deficiency caused proliferation arrest of pulmonary cells at E18.5-19.5. Similarly, Zfp148-deficient fibroblasts exhibited proliferative arrest that was dependent on p53, raising the possibility that cell stress is part of the underlying mechanism. Indeed, Zfp148 deficiency lowered the threshold for activation of p53 under oxidative conditions. Moreover, both in vivo and cellular phenotypes were rescued on Trp53(+/-) or Trp53(-/-) backgrounds and by antioxidant treatment. Thus, Zfp148 prevents respiratory distress and lethality in newborn mice by attenuating oxidative stress-dependent p53-activity during the saccular stage of lung development. Our results establish Zfp148 as a novel player in mammalian lung maturation and demonstrate that Zfp148 is critical for cell cycle progression in vivo

<i>Zfp148</i> deficiency prevented structural maturation of prenatal lungs without effecting epithelial cell differentiation or surfactant production.

<p>(<b>A</b>) Photomicrographs showing lung morphology (hematoxylin and eosin; HE) and glycogen content (periodic acid-Shiff; PAS) and CC10 immunofluorescence in P1 lungs from <i>Zfp148^gt/gt</i> and wt mice, respectively. (<b>A, B</b>) Graphs show quantification (<i>n</i> = 6) of mean tissue area per total lung area, PAS-positive area with bronchioles excluded, and CC10-positive area with bronchioles excluded in (A) P1 and (B) E19.5 lungs from wt and <i>Zfp148^gt/gt</i> mice. a.u., arbitrary units. (<b>C</b>) Real-time RT-PCR showing relative expression levels of markers for type I (T1alpha, Aqp5), type II (Sftpa1, Sftpb, Sftpc, Sftpd), clara (CC-10, Pon1), endothelial (Pecam1, Tie2, Nos3) and smooth muscle (Acta2) cells in <i>Zfp148^gt/gt</i> lungs compared to wt at P1 (<i>n</i> = 6). Wt means are represented by the horizontal straight line at 1. (<b>D</b>) Transmission electron microscope (TEM) image of <i>Zfp148^gt/gt</i> lung at E18.5–19.5 showing lamellar bodies secreted into the lumen of a terminal sac. (<b>E–G</b>) TEM images showing differentiated cells in <i>Zfp148^gt/gt</i> lungs at E18.5–19.5. (E) Apical part of an alveolar type II cell containing typical lamellar bodies (arrowheads), one of which is in the process of exocytosis (arrow), and accumulations of densely contrasted glycogen particles (asterisk). (F) Two ciliated cells (arrowheads) surrounding two Clara cells (arrows) with bulging appearance and mitochondria accumulated in the apical cytoplasm. (G) High power view of the blood-alveolar barrier showing an erythrocyte (asterisk) in close contact with a highly attenuated part of an endothelial cell that shares a basal lamina with the alveolar type I cell. Scale bars, 2 µm. *<i>P</i><0.05, ***<i>P</i><0.001.</p

<i>Zfp148</i> deficiency causes lethality in newborn mice and growth retardation and reduced life span in adult mice.

<p>(<b>A</b>) <i>Zfp148</i>-genotype distribution of offspring from heterozygous intercrosses. (<b>B</b>) Photograph of cyanotic <i>Zfp148^gt/gt</i> mouse and wt littermate at P1. (<b>C</b>) Body weight of wt, <i>Zfp148^+/gt</i> and <i>Zfp148^gt/gt</i> mice of mixed genders at E18.5–19.5 (<i>n</i> = 12 wt, 15 <i>Zfp148^+/gt</i>, 8 <i>Zfp148^gt/gt</i>), P1 (<i>n</i> = 9 wt, 13 <i>Zfp148^+/gt</i>, 7 <i>Zfp148^gt/gt</i>), P9 (<i>n</i> = 28 wt, 44 <i>Zfp148^+/gt</i>, 10 <i>Zfp148^gt/gt</i>) and P19–22 (<i>n</i> = 10 wt, 18 <i>Zfp148^+/gt</i>, 9 <i>Zfp148^gt/gt</i>). (<b>D, E</b>) Body weight curves for adult wt and <i>Zfp148^gt/gt</i> male (D) and female (E) mice, respectively (<i>n</i> = 10). (<b>F</b>) Kaplan-Meier plots showing survival of <i>Zfp148^gt/gt</i> and wt mice (<i>n</i> = 20). ***<i>P</i><0.001.</p

Deletion of one or two copies of <i>Trp53</i> rescued <i>Zfp148^gt/gt</i> mice from proliferation arrest, respiratory distress and neonatal lethality.

<p>(A) Photomicrographs showing BrdU labeling of E19.5 lung from wt, <i>Zfp148^gt/gt</i>, <i>Zfp148^gt/gtTrp53^+/−</i> and <i>Trp53^+/−</i> mice. Graphs show quantification of BrdU positive cells per lung area (<i>n</i> = 6 wt, 7 <i>Zfp148^+/gt</i>, 7 <i>Zfp148^gt/gt</i>, 5 <i>Zfp148^gt/gtTrp53^+/−</i>, 4 <i>Trp53^+/−</i>). (B) Photomicrographs showing lung morphology (hematoxylin and eosin; HE) and glycogen content (periodic acid-Shiff; PAS) and CC10 immunofluorescence in P1 lungs from <i>Zfp148^+/+Trp53^+/+</i> (<i>n</i> = 10), <i>Zfp148^gt/gtTrp53^+/+</i> (<i>n</i> = 9), <i>Zfp148^gt/gtTrp53^+/−</i> (<i>n</i> = 9), <i>Zfp148^gt/gtTrp53^−/−</i> (<i>n</i> = 5), and <i>Zfp148^+/+Trp53^−/−</i> (<i>n</i> = 10) mice, respectively. Graphs show quantification of mean tissue area per total lung area, PAS-positive area with bronchioles excluded, and CC10-positive area with bronchioles excluded. (C) Distribution of <i>Zfp148</i> genotypes of P1 pups of intercrosses between <i>Zfp148^+/gtTrp53^+/+</i> and <i>Zfp148^+/gtTrp53^+/−</i> mice. Scale bars, 100 µm. *<i>P</i><0.05, **<i>P</i><0.01, ***<i>P</i><0.001.</p

Antioxidant rescue of defect lung maturation and neonatal lethality in <i>Zfp148^gt/gt</i> mice.

<p>(<b>A</b>) Photomicrographs showing lung morphology (hematoxylin and eosin; HE) and glycogen content (periodic acid-Shiff; PAS) and CC10 immunofluorescence in P1 lungs from <i>Zfp148^+/+</i>, <i>Zfp148^gt/gt</i>, and NAC treated <i>Zfp148^gt/gt</i> mice, respectively (<i>n</i> = 6). Graphs show quantification of mean tissue area per total lung area, PAS-positive area with bronchioles excluded, and CC10-positive area with bronchioles excluded. (<b>B</b>) Distribution of <i>Zfp148</i> genotypes of P1 pups of intercrosses between <i>Zfp148^+/gt</i> mice with and without NAC treatment. Scale bars, 100 µm. **<i>P</i><0.01, ***<i>P</i><0.001.</p

Activation of p53 and <i>Trp53</i>-dependent proliferation arrest in <i>Zfp148^gt/gt</i> MEFs.

<p>(<b>A</b>) Western blots of MEF lysates showing expression of phospho-p53^Ser18 in wt and <i>Zfp148^gt/gt</i> MEFs cultured at 21 or 3% oxygen, respectively. <i>Trp53^−/−</i> cells were used as a negative control and actin was used as a loading control. Asterisk indicates unspecific band. (<b>B</b>) Real-time RT-PCR of <i>p21</i> in wt and <i>Zfp148^gt/gt</i> MEFs cultured at 21 or 3% oxygen, respectively, and on <i>Trp53^+/+</i>, <i>Trp53^+/−</i> and <i>Trp53^−/−</i> genetic backgrounds (<i>n</i> = 4). (<b>C, D</b>) CPD of <i>Zfp148^gt/gt</i> and wt MEFs on <i>Trp53^+/+</i> or <i>Trp53^−/−</i> (C) and <i>Trp53^+/+</i> or <i>Trp53^+/−</i> (D) genetic backgrounds (<i>n</i> = 3). (<b>E, F</b>) CPD of <i>Zfp148^gt/gt</i> and wt MEFs supplemented with <i>n</i>-acetyl-L-cysteine (NAC) (E) in the culture medium (<i>n</i> = 4), or cultured at atmospheric (21%) or low (3%) oxygen concentrations (F) (<i>n</i> = 3). *<i>P</i><0.05, **<i>P</i><0.01, ***<i>P</i><0.001.</p

How general are positive relationships between plant population size, fitness and genetic variation?

Relationships between plant population size, fitness and within-population genetic diversity are fundamental for plant ecology, evolution and conservation. We conducted meta-analyses of studies published between 1987 and 2005 to test whether these relationships are generally positive, whether they are sensitive to methodological differences among studies, whether they differ between species of different life span, mating system or rarity and whether they depend on the size ranges of the studied populations. 2 Mean correlations between population size, fitness and genetic variation were all significantly positive. The positive correlation between population size and female fitness tended to be stronger in field studies than in common garden studies, and the positive correlation between genetic variation and fitness was significantly stronger in DNA than in isoenzyme studies. 3 The strength and direction of correlations between population size, fitness and genetic variation were independent of plant life span and the size range of the studied populations. The mean correlations tended to be stronger for the rare species than for common species. 4 Expected heterozygosity, the number of alleles and the number or proportion of polymorphic loci significantly increased with population size, but the level of inbreeding FIS was independent of population size. The positive relationship between population size and the number of alleles and the number or proportion of polymorphic loci was stronger in self-incompatible than in self-compatible species. Furthermore, fitness and genetic variation were positively correlated in self-incompatible species, but independent of each other in self-compatible species. 5 The close relationships between population size, genetic variation and fitness suggest that population size should always be taken into account in multipopulation studies of plant fitness or genetic variation. 6 The observed generality of the positive relationships between population size, plant fitness and genetic diversity implies that the negative effects of habitat fragmentation on plant fitness and genetic variation are common. Moreover, the stronger positive associations observed in self-incompatible species and to some degree in rare species, suggest that these species are most prone to the negative effects of habitat fragmentation. © 2006 The Authors